code: def test_x_minus_y():
      f = 255 * np.random.random((128, 128))
      f = f.astype(np.uint8)
      h = mh.features.haralick(f, use_x_minus_y_variance=False)
      h2 = mh.features.haralick(f, use_x_minus_y_variance=True)
      assert np.sum(h != h2) == 4
  
imports: import numpy
  from mahotas.features import texture
  import mahotas
  import mahotas.features._texture
  import pytest
label_desc: Use image node_id 22 for calling a global function with example usage: test_x_minus_y() without return types